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MG Midget and Sprite Technical - Marina Gearbox

Would anyone be able to point to me any information about how to fit a Marina gearbox to a 1275 A-Series.

I've searched the archives but no luck.

A few years ago I found a website that described how to do it - but I can't find it now!

Thanks
Russell Morgan

To fit the single rail 'box, of the top of my head you will need:

Marina bell-housing. These are cast iron and HEAVY, however Chris Groves does a bespoke alloy one which many of the Class A racers use.

Marina back-plate - the starter motor is on the other side from the A series.

Marina Flywheel and clutch. The clutch is common to the midget 1500 and Spitfire 1500 and is a 23 spline design.
Deborah Evans

Russ
Please please satisfy my curiosity and tell us why you're doing that ????

I'm sure its not on the K though.

Ian
Ian Webb '73 GAN5

I've just realised I didn't say Marina box to MIDGET 1275 engine/crank in my question, the Marina engine/crank would obviously just fit the marina box.

Deborah, thanks. I have a memory that the Marina flywheel needs machining somewhere to accept the Midget crank, by 2mm I think. I think the locating dowels are different too (one has 1 the other 2). Not sure about the input shaft length/diameter/spigot bearing either.

Hey Ian, I hope all is well. A mate has a collection of Marina boxes sat around, he has modified the shell to accommodate the combination, we are just a little unsure what needs to be done inside the bellhousing.
He also likes the idea of a larger clutch, syncro on 1st and I think the Marina box is stronger, is it not?
Russell Morgan

Hmmm. I think you need to machine out a MIDGET flywheel to accept a Marina crank. so, doing the opposite - MARINA flywheel to Midget crank means either nothing has to be done, or it cant happen because the crank&flywheel won't locate properly. Hmmm.
Russell Morgan

Your other option is to modify the Midget flywheel to accept the 71/4" clutch. Or have a flywheel made.
Deborah Evans

Thanks for the input.

He's found someone who wants to swap their 1275 Marina engine for his Midget engine.

Problem solved!
Russell Morgan

Russ, Max has a good-ish Marina engine available...
David Smith

Thanks David.

The chap who has the Marina engine wants to swap it for a Midget crank & flywheel. We need to check but looking at the compression ratio that the pistons used on my mates spare 'Midget' crank would give, it may well be a Marina crank with Midget sized offset ground big ends. The spare crank comes from an engine used in Phil Isacc's yellow Midget racer you may remember from Wiscombe years ago. A bit of measuring needed I think. lol
Russell Morgan

This thread was discussed between 22/06/2011 and 23/06/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.